The present invention is related to a display device and a manufacturing method thereof, in particular to a technology effectively applied to a TFT (thin film transistor) liquid crystal display device and the manufacturing method of the same.
In the liquid crystal display device, there is an active matrix type liquid crystal display device in which active elements (also referred to as switching elements) are placed as matrix. For the active elements as described above TFT of MIS structure (including MOS structure) is used.
The active elements (TFT) in the active matrix type liquid crystal display device may have for example a semiconductor layer on the scan signal lines with a first insulation layer (gate insulation film) interposed therebetween. The drain region of the semiconductor layer in such a case may be connected to a drain electrode, which is branched from a video signal line. The source region of the semiconductor layer is connected to a source electrode, which may be formed at the same time as the video signal line. The source electrode is connected to a pixel electrode, which is formed on a second insulation layer, via a through hole.
The display area of the liquid crystal display device is formed of plural pixels, and the TFT and the pixel electrode are placed on each pixel.
One important thing when manufacturing the liquid crystal display device is for example to make uniform display characteristics of each pixel which compose one display area in one liquid crystal display panel.
When manufacturing a substrate used for the liquid crystal display panel to form the TFT thereon (referred to as a TFT substrate herein below), in general, scan signal lines, video signal lines, TFTs, pixel electrodes, etc. are formed on each of plural regions of one large plane glass substrate (mother glass), then the plural regions are cut out from the mother glass to obtain plural TFT substrates.
When manufacturing a TFT substrate used in a large liquid crystal display device such as a liquid crystal display television set or a personal computer display (monitor), a semiconductor layer, drain electrodes to be connected to the drain region of the semiconductor layer, and source electrodes to be connected to the source region of the semiconductor layer should be formed such that the size of TFT of each pixel which forms one display area on one TFT substrate will be the same size.
When manufacturing a TFT substrate for use in a small liquid crystal display device such as the display used in a cellular phone terminal or in a PDA, for plural TFT substrates obtained from one mother glass, a semiconductor layer, drain electrodes to be connected to the drain region of the semiconductor layer, and source electrodes to be connected to the source region of the semiconductor layer should be formed such that the size of TFT elements formed on the display area of each TFT substrate will be the same size.